Storage climate

Storage climate refers to the temperature, humidity, and general environmental conditions in whisky storage facilities and describes how these conditions affect stored casks and their contents over time.

Key parameters

• Temperature: The average temperature and its variations determine the rate of wood exchange and alcohol diffusion. Many traditional warehouses operate at moderate temperatures, typically around 12–18°C, with small daily fluctuations to avoid large expansions and contractions of the wood.

• Relative humidity (RH): RH affects the wood's expansion and the seal density between the cask and the cork, as well as water and alcohol exchange. RH is often in the 60–70% range, but can vary ±5–10% depending on building and climate.

• Variation and stability: Aim to minimize large swings, as constant conditions yield more predictable maturation and less risk of leakage or uneven development of flavor and color. Microclimates between different rooms within the same warehouse can create different maturation profiles.

Impact on storage and maturation

• Wood and contents: Temperature affects diffusion and extraction of aromas such as vanillin, lignins and tannins from the oak. Higher temperatures generally accelerate maturation, while lower temperatures slow the pace.

• Humidity and density: RH affects the wood's expansion and the density around the cask seals. Too high RH can increase the risk of condensation, mold and leaks; too low RH can cause the wood to shrink and increase the risk of loose staves and altered density.

• Evaporation (angel's share): The evaporation of water and alcohol depends on temperature and RH; higher average temperature increases evaporation, altering the whisky concentration over time.

Practical controls and operations

• Monitoring: Regular measurement of temperature and RH with calibrated thermometers and hygrometers; data logging enables identification of unwanted patterns.

• Climate control: Stable ventilation, adequate insulation and, where relevant, air conditioning or dehumidification to maintain desired ranges. Limit direct light and vibrations, which can affect maturation and quality.

• Warehouse design: Planning of rooms and capacity to achieve uniform microclimate; differences between room levels should be considered if a uniform maturation profile is required.

Special considerations for casks and storage

• Tightness and closure: Good control of the cask tightness and cork or rubber gaskets to reduce unwanted evaporation and leakage.

• Storage duration and style: Climate differences can encourage different stylistic expressions in the whisky's color, aroma and flavor.